Mass spectrometry is being employed as a structural and analytical aid in investigations of the antibiotics aureofungin, vacidin A, candimycin, hamycin, scopafungin, saramycetin, and zervamicin, as well as of an antiviral substance from the streptovaricin complex, and complex mixtures of antibacterial, antifungal, antitumor and antiviral compounds from marine organisms. Field desorption, field ionization and chemical ionization mass spectrometry are under study, employing high resolution as well as capillary and packed column gas chromatographic techniques.